Video: Pack 1 • Paper 1 • Question 1

Pack 1 • Paper 1 • Question 1

02:35

Video Transcript

The scatter graph shows the number of ice creams sold per day from an ice cream van and the maximum daily temperature. One of the points is an outlier. State the coordinates of the outlier.

An outlier, sometimes called an anomaly, is a value that is noticeably smaller or larger than the rest of our results. We sometimes choose to omit these when analyzing our data, if they are likely to significantly change, for example, the value of the mean.

You’ll need to use your judgement here and look for the coordinate that seems to be out of place. In this case, that coordinate lies at 20, 10. The coordinate of the outlier is 20, 10.

What type of correlation is shown for the rest of the points? Notice how this question is asking you to describe the type of correlation the data is showing you. It is, therefore, not enough to say as the temperature increased, so did the number of ice creams sold. We have to use the word “positive,” “negative,” or “no correlation.”

In fact, this is an example of positive correlation. We know because the line of best fit would slope upwards. A scatter graph with negative correlation would have a line of best fit sloping downwards.

Estimate the number of ice creams sold on a day with a maximum temperature of 15 degrees Celsius. Notice how part c has two potential marks available for it. It is really useful to get into the habit of drawing a line of best fit for scatter diagram questions, as this is where the first mark will be awarded. Then and only then can you read your values from the graph.

Here we find 15 degrees on the 𝑥-axis and draw a line up until we meet our line of best fit. Then we draw a horizontal line from this point to the 𝑦-axis. You can see, therefore, that an estimate for the number of ice creams sold is 21.

Michael states that more ice creams are sold on warmer days. Does the scatter graph support his claim? Give a reason to support your answer.

You have a number of options with regards to how you choose to word this question. However, when we are interpreting scatter diagrams, it is useful to describe the correlation and what it means in the context of the question. Here the graph shows a positive correlation, meaning that the higher temperature will indeed lead to a larger number of ice creams sold.